Deprecate sphinx.io.FiletypeNotFoundError and get_filetype()

CHANGES

@@ -10,6 +10,9 @@ Incompatible changes
 Deprecated
 ----------
 
+* ``sphinx.io.FiletypeNotFoundError``
+* ``sphinx.io.get_filetype()``
+
 Features added
 --------------
 

doc/extdev/deprecated.rst

@@ -26,6 +26,16 @@ The following is a list of deprecated interfaces.
      - (will be) Removed
      - Alternatives
 
+   * - ``sphinx.io.FiletypeNotFoundError``
+     - 2.4
+     - 4.0
+     - ``sphinx.errors.FiletypeNotFoundError``
+
+   * - ``sphinx.io.get_filetype()``
+     - 2.4
+     - 4.0
+     - ``sphinx.util.get_filetype()``
+
    * - ``sphinx.builders.gettext.POHEADER``
      - 2.3
      - 4.0

sphinx/io.py

@@ -19,7 +19,10 @@ from docutils.statemachine import StringList, string2lines
 from docutils.transforms.references import DanglingReferences
 from docutils.writers import UnfilteredWriter
 
-from sphinx.deprecation import RemovedInSphinx30Warning, RemovedInSphinx40Warning
+from sphinx.deprecation import (
+    RemovedInSphinx30Warning, RemovedInSphinx40Warning, deprecated_alias
+)
+from sphinx.errors import FiletypeNotFoundError
 from sphinx.transforms import (
     AutoIndexUpgrader, DoctreeReadEvent, FigureAligner, SphinxTransformer
 )
@@ -335,3 +338,11 @@ def read_doc(app, env, filename):
 
     pub.publish()
     return pub.document
+
+
+deprecated_alias('sphinx.io',
+                 {
+                     'FiletypeNotFoundError': FiletypeNotFoundError,
+                     'get_filetype': get_filetype,
+                 },
+                 RemovedInSphinx40Warning)